The Study On Thermal Characteristics Analysis Of Hermetically Sealed Electromagnetic Relays

The thermal characteristic analysis of hermetically sealed electromagnetic relays is one of the most important contents about its reliability design. With the development of relay manufactory, the volume of the hermetically sealed electromagnetic relay tends to be small and qualifications and reliability indexes increases widely. The increase of heat productivity per unit volume can result in inner parts overheating. Specially, the huge heat result from electric arc discharging will cause contact material ablation and damage more severely, which influences the life of relays and work reliability directly. So the steady-state and transient-state heating problem has become an important aspect of its design process.In the past, thermal circuit method is used to resolve the hermetically sealed electromagnetic relay's thermal field, but for the relay's complex structure and the simple model built, so the result is inaccuracy. Analyzing exiting studying state, this paper use Finite Element Method (FEM) to resolve the thermal characteristic of the hermetically sealed electromagnetic relay and obtain temperature rise of key components in the relay.Firstly, the mathematic model for the relay's thermal field is established and is deduced to the Finite Element mathematic model with variational principle. A Finite Element Method analysis software-ANSYS is used to resolve the model. The convection coefficient is calculated through thermal associated expression. Through researching heat transfer mechanisms of sealed-in gases, it is thus sufficient to consider thermal conduction only. ANSYS is used to calculate outer wire's thermal effect to thermal field in the relay. The method of applying coil and contact resistance heating load is considered, respectively. At last, to verify the accuracy of the result, an infrared (IR) camera is used to do the experiment. The calculation result is compared with the test result, which proves the validity of the thermal field mathematic model of the hermetically sealed electromagnetic relay.Secondly, a mechanical, electrical and thermal coupled field simulation analysis of contact system of sealed electromagnetic relays is carried out through finite element software ANSYS. The heat distribution and current density distribution of contact system is gained. And the effect of contact force and outer diameter of the connecting wires is analyzed. In addition, because of the arc between the contacts, the material of contacts occur phase change, such as melting, vaporizing etc. This process is analyzed, and the transient temperature distribution of the arc spot and its near area is gained.This research can not only provide theory foundation for the reliability design of hermetically sealed electromagnetic relays, but also be available to the thermal characteristic analysis of other sealed apparatus and electron products.